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Different mechanisms are responsible for the contractile effects of histaminergic compounds on isolated intestinal smooth muscle cells
No full textThe effects of histamine and dimaprit on intestinal smooth muscle contractility were investigated on isolated cells from longitudinal muscle of the guinea pig ileum. Both histamine (10(-14)-10(-10) M) and dimaprit (10(-13)-10(-10) M) exerted a concentration-dependent contraction of intestinal cells, causing a maximum decrease in cell length of about 20%. This effect was not significantly different from that induced by cholecystokinin-octapeptide (CCK-8) 10(-9) M. The concentration-response curves to histamine and dimaprit were shifted to the left in the presence of the histamine H-2-receptor antagonist famotidine (10(-7) M) indicating the occurrence in the smooth muscle of H-2 receptors mediating relaxation. Whereas the contraction produced by histamine was competitively antagonized by the HI receptor antagonist mepyramine (10(-8) M), neither mepyramine (10(-7) M) nor temelastine (10(-7) M) did modify the contractile effect of dimaprit. In contrast, atropine (10(-8) M) significantly depressed the maximum response to dimaprit without affecting that exerted by histamine. These data indicate that histamine and dimaprit can modify intestinal contractility, by acting via different mechanisms; while the contractile action of histamine is related to H-1 receptor activation, that produced by dimaprit involves cholinergic pathways
Contractile and relaxant effects of dimaprit on guinea pig isolated intestinal cells
No full textThe effect of the histamine H-2 receptor agonist dimaprit on intestinal contractility was characterized on smooth muscle cells isolated from the longitudinal muscle of the guinea pig ileum. Dimaprit exerted two opposite effects on the contractility of isolated muscle cells. relaxation of cholecystokinin octapeptide (CCK-8)-induced contractions in the range of concentrations 10(-17)-10(-13) M and contraction at concentrations higher than 10(-13) M. The relaxant effect of dimaprit was totally prevented by the H-2 blocker famotidine (10(-7) M), which, at the same time, enhanced the contractile effect of dimaprit, shifting to the left the concentration-response curve to the agonist. This contraction was not modified by the histamine H-1 receptor antagonists pyrilamine and temelastine, tested both at 10(-7) M. By contrast, atropine 10(-8) M abolished the contractile effect of dimaprit, while leaving unchanged the response to CCK-8. Our results clearly indicate that longitudinal muscle cells of the guinea pig ileum possess inhibitory H-2 receptors, which can be activated by very low concentrations of dimaprit; moreover, they revealed that dimaprit can have non-histaminergic effects, probably due to muscarinic receptor activation; however, concentrations about 10000 times higher than those necessary to activate Hz receptors,are require
Exogenous and endogenous compounds which affect the contractility of the lower esophageal sphincter (LES).
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The contractile effect of fedotozine on guinea pig isolated intestinal cells is not mediated by kappa opioid receptors
No full textThe compound fedotozine, recently described as a peripheral kappa opioid receptor agonist, was tested on smooth muscle cells isolated from the longitudinal muscle layer of the guinea pig ileum, in comparison with the selective kappa receptor agonist, compound U-50488. Fedotozine (1 nmol/l - 1 mu mol/l) caused a concentration-dependent contraction of intestinal cells, with a maximum decrease in cell length not significantly different from that caused by acetylcholine. The kappa agonist U-50488 (0.1 pmol/l-100 nmol/l) was without effect. The contractile effect of fedotozine was not significantly modified by naloxone (0.1-1 mu mol/l). These results indicate that fedotozine can have direct excitatory effects on intestinal smooth muscle cells from the guinea pig ileum not mediated by activation of kappa opioid receptors
Characterization of histamine H_2-receptors in human neutrophils with a series of guanidine analogues of impromidine: Are cell type-specific H_2-receptors involved in the regulation of NADPH oxidase?
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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